A known autostereoscopic display device is described in the paper entitled “Multiview 3D-LCD” by C. van Berkel et al. in SPIE Proceedings, Vol. 2653, 1996, pages 32-39. This known device comprises a two dimensional liquid crystal display panel having a row and column array of display pixels acting as a spatial light modulator to produce the display. An array of elongate lenticular elements extending parallel to one another overlies the display pixel array, and the display pixels are observed through these lenticular elements.
The lenticular elements are provided as a sheet of elements, each of which comprises an elongate semi-cylindrical lens element. The lenticular elements extend in the column direction of the display panel, with each lenticular element overlying a respective group of two or more adjacent columns of display pixels.
In an arrangement in which, for example, each lenticule is associated with two columns of display pixels, the display pixels in each column provide a vertical slice of a respective two dimensional sub-image. The lenticular sheet directs these two slices and corresponding slices from the display pixel columns associated with the other lenticules, to the left and right eyes of a user positioned in front of the sheet, so that the user observes a single stereoscopic image.
In other arrangements, each lenticule is associated with a group of four or more adjacent display pixels in the row direction. Corresponding columns of display pixels in each group are arranged appropriately to provide a vertical slice from a respective two dimensional sub-image. As a user's head is moved from left to right a series of successive, different, stereoscopic views are perceived creating, for example, a look-around impression.
The above described device provides an effective three dimensional display. However, it will be appreciated that, in order to provide stereoscopic views, there is a necessary sacrifice in the horizontal resolution of the device. For example, a display panel having an array of 600 rows and 800 columns of display pixels may provide a four-view autostereoscopic display in which each view comprises an array of 600 rows and 200 pixels. This substantial difference between vertical and horizontal resolution is undesirable.
U.S. Pat. No. 6,064,424 discloses an autostereoscopic display device similar to that described above, except that the elongate lenticular elements are slanted at an angle to the column direction of the display panel. By slanting the lenticular elements, some of the reduction in horizontal resolution, which would otherwise be required, is transferred to the vertical resolution. It thus becomes possible to “consume” both vertical and horizontal resolution to increase the number views displayed by the device.
Since the displays are intended to be viewed by persons standing or sitting in an upright position, they are designed such that the views extend mainly in the horizontal direction. For this reason, the slant direction of the cylindrical lenses is chosen such that the angle between the lenses and the vertical direction is relatively small. The almost vertical lenses combined with the favorable horizontal-to-vertical aspect ratio of the sub-pixels (1:3 for most panels), yields a good view separation and a good pixel structure. As a consequence, these products are particularly suitable for use in “landscape” mode.